The effect of electronic structure changes in NaInO2 and NaIn0.9Fe0.1O2 on the photoreduction of methylene blue

Abstract

Photochemical dye degradation is a promising method for organic pollutant remediation; however, this process has been limited by the efficiency of the catalyst materials with respect to photon absorption. An ideal catalyst would be capable of using as much of the solar spectrum as possible, in particular the visible region. One interesting class of materials that have the potential to provide this photoactivity is known as delafossites. These materials have the general formula ABO₂ and are based on the mineral CuFeO₂, also known as delafossite. They are especially interesting due to the ability to alter the band structure of these materials using chemical substitution. In particular, substitution on the B-site in these materials can be used to tune the physical properties of delafossites for specific applications. In this work, NaInO₂ and NaIn_0.9Fe_0.1O₂ have been studied and Fe substitution was found to decrease the band gap energy from 3.9 eV to 2.8 eV. The catalytic activity, measured by methylene blue dye degradation, of these delafossite materials was analysed and the reduction in band gap energy was found to result in increased visible light photoactivity. Computationally, thousands of supercells were examined in order to determine the most energetically favourable substituted structures and generate density of states plots in order to determine that the experimentally observed results were due to Fe-states increasing the energy of the highest occupied molecular orbitals.